1. Field of the Invention
The present invention relates to liquid dispensing, particularly of viscous liquids such as liquid soap.
2. Background Information
The conservation and sanitary advantages of automatic flow control in sinks and similar installations are well known, so many public rest-room facilities have provided automatic faucets and flushers. Although there is a similar advantage to making liquid soap dispensing automatic in such installations, the popularity of doing so has not been particularly great so far.
Much of the reason for this slow acceptance is installation difficulty. Installing a liquid-soap dispenser often requires providing extra wiring. One solution to this problem is to employ battery-operated systems. This approach is now popular for retrofitting manual flushers to make them automatic, but the power required to pump liquid soap, which can be fairly viscous, is significant. This tends to make battery life in liquid-soap dispensers too short unless the batteries are unacceptably large.
As the above-mentioned Parsons et al. application for a Pressure-Compensated Liquid Dispenser indicates, we have recognized that reasonable-size batteries can afford acceptable longevity if the pumping energy is provided in the form of a pressurized fluid in refill soap containers. The pressure in the container is adequate to force the viscous liquid through the dispenser outlet at an acceptable rate, so electric (typically battery) power is needed only for flow control, not to propel the viscous liquid soap.
We have recognized that this concept can be improved by adapting a concept used in some other dispensing contexts, namely, to provide the pressurizing fluid in a container separate from the liquid to be dispensed. The container for the liquid soap or other liquid to be dispensed will tend to be considerably larger but under much lower pressure than the other container, which is a cartridge that contains the pressurizing fluid and may itself be enclosed by the other container. The cartridge contains a substance under high pressure that can be released as a gas into the liquid container to pressurize the liquid in its reservoir. The pressurizing gas flows as needed by way of a pressure regulator. The pressure regulator permits pressurizing gas to flow from the cartridge into the liquid container only so long as the resultant reservoir pressure does not exceed a predetermined limit value, which is less than the pressure that the cartridge supplies. The resultant pressure urges the liquid through an outlet in the liquid container. By storing the pressurizing fluid separately from the liquid to be dispensed, we significantly reduce the size and/or strength required of the liquid container.
In accordance with one aspect of the invention, that flow is controlled in response to an object sensor. For instance, a control circuit can permit soap flow when the sensor detects a user""s hand near the outlet.